// 直接在0到x范围内找平方小于等于x的最大整数
// 求mid的时候记得+1
class Solution {
    public int mySqrt(int x) {
        if (x == 0) return 0;
        long left = 1, right = x;
        while (left < right) {
            long mid = left + (right - left + 1) / 2;
            if (mid*mid > x) {
                right = mid - 1;
            } else {
                left = mid;
            }
        }
        return (int)left;
    }
}